1. Field of the Invention
The present invention relates to an apparatus for inspecting a thin film pattern formed on a substrate, and more particularly to a light device that is used for arranging a sensor array which is for continuously taking photographs of a thin film pattern for each line.
2. Description of the Related Art
Thin films are formed in a shape of being designed in multi-layers on a bared substrate, a wafer or a glass substrate to realize a printed circuit board, a semiconductor integrated circuit and a pixel driving circuit which drives pixel cells of a display device such as a liquid crystal display panel and a plasma display panel. In the thin film pattern, a minute defect or spot of a few micrometers μm or less can be generated in a process that the thin film formed on a substrate is patterned by a chemical etching process or a patterning process using laser beam.
The defect on the thin film pattern such as the minute defect or spot is detected by a process of photographing the surface of the substrate to make out the state of the photographed thin film pattern. An inspection apparatus used for detecting the defect on the thin film pattern includes a sensor array which photographs the substrate surface for each line so as to shorten the inspection time. The sensor array includes charge coupled devices (hereinafter, referred to as “CCD”) and lenses for controlling the focus condition of each CCD. In order for the thin film pattern inspection apparatus inclusive of the sensor array to correctly detect the minute defect on the thin film pattern, an optimal focus condition of the sensor array is set in accordance with an inspection resolution as well as a coordinate system of an image generated by the sensor array and a coordinate system of a real inspection subject are to be mapped to be identical, and further the sensor array should be arranged so that an incident light to the sensor array is made to be uniform.
As a method for arranging the thin film pattern sensor array in an optimal condition, the printed circuit board inspection apparatus uses a pattern film 10 where a first black bar 12 and a second black bar 14 are printed to be mixed in a parallel direction, as shown in FIG. 1. The first black bar 12 represents a logic value ‘2’ on its surface and the second black bar 14 represents a logic value ‘5’. The method controls a location and posture of each of the CCD and lens included in the sensor array in accordance with a surface condition of the pattern film 10 which is photographed by the sensor array while the pattern film 10 is fed to a reverse direction to a photographing direction of the sensor array for inspecting the printed circuit board. In this method, because a coordinate values “Rθ Φ” shown in relation to the focus of the CCD for each pixel and a start position of an image cannot be obtained, there is required an arrangement process for a separate minute adjustment.
Differently from the arrangement method of the sensor array for inspecting the printed circuit board, as a method of making it possible to minutely arrange the sensor array on the basis of the focus of the CCD for each pixel and the start position of the image, there is an arrangement method of the sensor array for inspecting the display device which uses a correction pattern film 20 shown in FIG. 2. The correction pattern film 20 includes a resolution measuring pattern 22 formed to have scales of a fixed width in a fixed gap at a left edge of its own surface; and a left-right rotation correction pattern 24 formed to have thin and thick bars at the right side of the resolution measuring pattern 22. Further, patterns 26 for another inspection purpose are formed in the remaining area of the right side of the left-right rotation correction pattern 24 on the correction pattern film 20. The correction pattern film 20 as shown in FIG. 2, is fed to the reverse direction to the photographing direction of the sensor array on a light irradiating plane of the arrangement apparatus of the sensor array for inspecting the display device, thus the posture and position of each CCD and the position of each lens which are included in the sensor array can be controlled in accordance with the state of the correction pattern film 20 which is photographed by the sensor array.
In addition, the arrangement apparatus of the sensor array for inspecting the display device using the correction pattern film 20 of FIG. 2 includes a sensor array 30 and an light source 32 which are located to be symmetric in the right side and the left side of an irradiation datum plane 36, as shown in FIG. 3. The irradiation datum plane 36 is located in a correction target area 38 on a light irradiation plane 34 to be perpendicular to the light irradiation plane 34. The light irradiation plane 34 guides the thin film substrate of the display device when inspecting the thin film pattern of the display device, and it guides the correction pattern film 20 of FIG. 2 which is fed from the light source 32 to the sensor array 30 when arranging the sensor array.
When arranging the sensor array 30, the correction pattern film 20 of FIG. 2 is fed to the reverse direction to the photographing direction of the sensor array 30 on the light irradiation plane 34 of the arrangement apparatus of the sensor array for inspecting the display device, thus the posture and position of each CCD and the position of each lens which are included in the sensor array 30 can be controlled in accordance with the state of the correction pattern film which is photographed by the sensor array 30. The resolution measuring pattern 22 allows an adjuster (or an adjustment processor) to confirm the dimension of the surface of the pattern correction film 20 which is photographed by each CCD of the sensor array 30, thereby enabling to control the resolution. The left-right rotation correction pattern 24 allows an adjuster (or an adjustment processor) to confirm a point which is first photographed by each CCD of the sensor array 30, thereby enabling to correct a relative location of the sensor array 30 to the correction pattern film 20 and to correct a location of each CCD in an X-axis direction and a rotation amount Rθ Φ thereof for the X-axis within the sensor array. Herein, values in an X axis and an Y axis determine a start position of an image to be obtain from the subject, and a value in a Z-axis determines the focus of the image. The values are the measured amounts which uniformly appear over all the area of the sensor array, thus the location and posture of the sensor array is adjusted on the basis of the subject to adjust the values.
In this way, the prior method and apparatus for arranging the sensor array for inspecting the thin film pattern require a correction pattern film 20 which is separately made in accordance with the inspection subject and the resolution required by the inspection subject. For an optimal arrangement of the sensor array 30, a distribution of a light irradiated from the light source 32 should be evenly kept in a section from one end of the light source 32 to the other end thereof. However, the light irradiated in the section from the one end of the light source 32 to the other end in the prior arrangement apparatus of the sensor array for inspecting the thin film pattern is not uniformly distributed, as shown in FIG. 4A. In addition to this, the distribution of the light irradiated from the light source 32 to the correction target area 38 on the light irradiation plane 34, as shown in FIG. 4B, is hard to be evenly kept over all the section from one end of the correction target area 38 to the other end thereof. The uniformity of the light distribution and the correction pattern film 20 becomes worse as the thin film pattern is made in a large size because the liquid crystal display panel and the plasma panel are large-sized.